Nickel base alloy

ABSTRACT

THE PRESENT INVENTION CONTEMPLATES NICKEL-BASE ALLOYS CONSISTING IN PRESENT BY WEIGHT ESSENTIALLY OF ABOUT 0.1% TO ABOUT 0.25% CARBON, ABOUT 7.5% TO ABOUT 10% CHROMIUM, ABOUT 0.75% TO ABOUT 2% TITANIUM, ABOUT 5% TO ABOUT 6.25% ALUMINUM, ABOUT 8% TO ABOUT 12% COBALT, ABOUT 8% TO ABOUT 12% TUNGSTEN, ABOUT 0.8% TO ABOUT 2.5% HAFNIUM, ABOUT 0.002% TO ABOUT 0.2% BORON, UP TO ABOUT 0.15% ZIRCONIUM, ABOUT 1.5% TO ABOUT 3.5% TANTALUM, ABOUT 0.2% TO ABOUT 0.9% MOLYBDENUM, WITH THE BALANCE BEING ESSENTIALLY NICKEL.

United States Patent Office 3,720,509 Patented Mar. 13, 1973 3,720,509 NICKEL BASE ALLOY Wilbert P. Danesi, Deerfield, Ill., and Rudolf H. Thielemann, Portland, reg., assignors to Martin Metals Company, Wheeling, Ill. No Drawing. Filed Dec. 14, 1970, Ser. No. 98,013 Int. Cl. C22c 19/00 U.S. Cl. 75171 4 Claims ABSTRACT OF THE DISCLOSURE The present invention contemplates nickel-base alloys consisting in percent by weight essentially of about 0.1% to about 0.25% carbon, about 7 to about 10% chromium, about 0.75% to about 2% titanium, about 5% to about 6.25% aluminum, about 8% to about 12% cobalt, about 8% to about 12% tungsten, about 0.8% to about 2.5% hafnium, about 0.002% to about 0.2% boron, up to about 0.15% zirconium, about 1.5% to about 3.5% tantalum, about 0.2% to about 0.9% molybdenum, with the balance being essentially nickel.

In U.S. patent application Ser. No. 841,505, now abandoned, copending herewith (and filed on July 14, 1969 as a continuation-in-part of U.S. application Ser. No. 725,- 074, filed on Apr. 29, 1968, now abandoned), it is disclosed that nickel-base alloys within the following tabulated ranges of percent by weight are highly advantageous for use in gas turbine structures such as turbine blades:

1 Balance essentially and includes small amounts of unavoidable impurities and incidental elements.

Particular alloys Within this range can possess compositions in percent by weight, as disclosed in U.S. application Ser. No. 841,505, now abandoned, as follows:

0. 05 0. 05 0. 015 0. 015 1 Bal. E 1 Bal. E

1 Hal. E =Balanee Essentially and includes small amounts of unavoidable impurities and incidental elements.

It is disclosed in application Ser. No. 841,505, now abandoned that lowering the molybdenum content from 2.5% by weight in alloy A to 0% by weight as in alloy B coupled with an increase in hafnium content from 1.5 to 2.5% results in an alloy having highly advantageous impact resistance characteristics. Following this approach further,

it has now been discovered that by maintaining the elements molybdenum, hafnium and tantalum within very restricted ranges in the general type of nickel-base alloy, as exemplified by alloy A, highly advantageous commercial alloys can be provided.

It is an object of the present invention to provide highly advantageous, commercial, nickel-base alloys, which are mechanically stable after long time exposure at elevated temperatures.

Other objects and advantages will become apparent from the following description.

Generally speaking, the present invention contemplates nickel-base alloys consisting in percent by weight essentially of about 0.1% to about 0.25% carbon, about 7.5% to about 10% chromium, about 0.75% to about 2% titanium, about 5% to about 6.25% aluminum, about 8% to about 12% cobalt, about 8% to about 12% tungsten, about 0.8% to about 2.5% hafnium, about 0.002% to about 0.2% boron, up to about 0.15% zirconium, about 1.5 to about 3.5% tantalum, about 0.2% to about 0.9% molybdenum, with the balance being essentially nickel. Advantageously, the tantalum content of the alloys is about 3.0%, the total of the aluminum plus titanium percentages is about 7% and the molybdenum content of the alloys is within the range of about 0.5% to about 0.7%.

An illustrative alloy of the present invention consists essentially of about 0.15% carbon, about 9% chromium, about 0.7% molybdenum, about 1.5% titanium, about 5.5% aluminum, about 10% cobalt, about 10% tungsten, about 1.5 hafnium, about 0.02% Zirconium, about 0.015% boron, about 2.5 tantalum, with the balance being essentially nickel. This alloy, when cast into gas turbine structures, gives parts characterized by a high combination of characteristics of impact resistance, high and intermediate temperature strength and ductility, reproducibility, resistance to thermal fatigue and the like.

The following data obtained on representative cast-tosize samples of the alloy of the present invention show the utility of the alloy of the present invention with respect to various mechanical characteristics of engineering significance. These data were obtained on samples of the alloy which had been heated for 50 hours at 1550 F.

When tested in stress-rupture mode at 1600 F. (871 C.) under a load of 40,000 pounds per square inch (p.s.i.) (2812 kilograms per square centimeters [kg./cm. the alloy of the present invention had a life of 2335 hours with an elongation of 8.5%. In contrast, under the same conditions, alloy B had a life of only about 444 hours with an elongation of only 6.0%.

When tested in stress-rupture mode at 1800 F. (982 C.) under a load of 34,000 p.s.i. (2390 kg./cm. the alloy of the present invention had a life-to-rupture of 39.9 hours and an elongation of 7.5 This result is a substantial improvement as compared to results obtained with alloy B tested under the same conditions.

Again when tested in stress-rupture mode at 1400 F. (760 C.) under a load of 105,000 p.s.i. (7381.5 kg./ cm?) the alloy of the present invention exhibited a lifeto-rupture of 143.9 hours and a percent prior creep (measured about 2 hours prior to rupture) of 2.58%. This result is at least equivalent to the results obtained with alloy B tested under the same conditions.

The following table sets forth in English and metric units the result of tensile tests performed on the alloy of the present invention at room temperature:

Percent Elon- Reduction Ultimate tensile strength 0.2 yield strength gation in area 163,000 p.s.l 143,000 p.s.i- 4. 5 9. 0 11,450 kgJcmfl 10,050 kgJcmfl... 4. 5 9. 0

The foregoing data show that the alloy of the present invention is a highly advantageous, commercially acceptable alloy especially in view of the fact that the alloy of the present invention exhibits high impact strengths of the order of about 25 foot-pounds or higher which impact strengths are relatively unaffected by exposure to high temperature for extended periods of time. The alloy of the present invention is also characterized by high resistance to thermal fatigue and high reproducibility from heat to heat.

Specific examples of alloys within the ambit of the present invention are set forth (in percent by weight) in the following table:

TABLE Example l 1 2 3 4 5. 35 5. 5O 5. 53 5. 8 0.015 0. 02 0.017 0. 014 O. 15 O. 16 0. 16 0. 11 9. 92 10. 9. 98 8. 7. 93 8. 25 8. 07 9. 0 0. 70 0. 7 0. 67 0. 5 Ba]. Bal. Bal. Bal. 3. 13 3. 0 3. 06 3.3 1. 49 1. O 1. 06 0. 8 9. 65 10. O 9. 90 10. 5 0. 05 0 09 0. 11 0. 1. 58 1. 6 1. 56 1. 3

The alloys of the present invention are advantageously melted and cast under vacuum using investment casting techniques. Those skilled in the art will appreciate that the alloys of the invention can contain small amounts of incidental elements and impurities along with and encompassed within the term balance nickel. Such impurities and incidental elements should be maintained at as low a level practical considering the needs of commercial production. The alloys of the present invention, while being particularly adapted for use as cast gas turbine components, such as turbine blades and the like, can be used also with advantage in any area of utility where strength at elevated temperatures is a necessary criterion.

While the present invention has been described in conjunction with advantageous embodiments, those skilled in the art will recognize that modifications and variations may be resorted to Without departing from the spirit and scope of the invention. Such modifications and variations are considered to be within the purview and scope of the invention We claim:

1. A nickel-base alloy consisting essentially in percent by weight of about 0.1% to about 0.25% carbon, about 7.5% to about 10% chromium, about 0.75% to about 2% titanium, about 5% to about 6.25% aluminum, the total of the percentages of aluminum plus titanium being at least 6.5%, about 8% to about 12% cobalt, about 8% to about 12% tungsten, about 0.8% to about 2.5% hafnium, about 0.002% to about 0.2% boron, up to about 0.15% zirconium, about 1.5% to about 3.5% tantalum, about 0.2% to about 0.9% molybdenum, with the balance being essentially nickel.

2. An alloy as in claim 1 wherein the tantalum content is about 3%.

3. An alloy as in claim 1 wherein the molybdenum content is about 0.5% to 0.7%.

4. An alloy as in claim 1 wherein the percent aluminum plus the percent titanium is about 7% References Cited UNITED STATES PATENTS 3,479,157 11/1969 Richards et a1 171 RICHARD O. DEAN, Primary Examiner 

